Gamma (Option Greek)
Gamma is the second-order Greek that measures how quickly an option’s Delta changes as the underlying moves. It is most important for traders running short-dated, ATM options where a few points of underlying movement can shift the option’s behaviour significantly. Understanding gamma helps Indian options traders manage explosive risk near expiry.
Key takeaways:
- Gamma measures the rate of change of Delta per unit move in the underlying.
- ATM options have the highest gamma; deep ITM and OTM have low gamma.
- Gamma is highest near expiry — gamma risk peaks in the last week of weekly options.
- Long options have positive gamma; short options have negative gamma.
- Negative gamma exposure (short options near expiry) can cause severe losses on sudden moves.
Intuition behind gamma
Delta describes how much the option premium moves with the underlying — but delta itself changes. Gamma quantifies how delta evolves. A high-gamma option behaves dramatically as the underlying moves: its delta accelerates from 0.5 to 0.8 quickly with a favourable move, or collapses to 0.2 with an unfavourable one.
Where gamma is highest
- ATM strikes: Maximum sensitivity to underlying moves.
- Short-dated options: Less time means more sensitivity per unit move.
- High-IV environments: Premiums fluctuate dramatically with underlying moves.
Long vs short gamma
| Long gamma (long options) | Short gamma (sold options) | |
|---|---|---|
| Delta exposure | Increases in favourable direction | Increases against you |
| Risk profile | Limited (premium paid) | Unlimited if naked |
| Best in | Volatile environments | Quiet, range-bound markets |
Gamma risk near expiry
On expiry day, a near-ATM option’s gamma can spike dramatically. A sudden 100-point Nifty move can flip a near-ATM short call from breakeven to a deep loss in minutes. This is why naked option selling is dangerous in the final hours of weekly expiries — gamma risk overwhelms theta gains.
Practical applications
- Sell options with lower gamma (deeper OTM, longer expiry) for safer income strategies.
- Buy ATM short-dated options to benefit from gamma in expected moves.
- Use gamma-scalping strategies — delta-hedge long-gamma positions to harvest volatility.
- Monitor portfolio gamma to anticipate sudden delta swings.
Gamma and the option chain
Most modern Indian charting platforms display Gamma alongside Delta in the option chain. Traders use this column to identify which strikes are most explosive in either direction. A simple rule of thumb: highest gamma corresponds to highest implied move per rupee of premium.
Frequently asked questions
Is gamma always positive?
For long option positions yes; for short positions, position gamma is negative.
Why is gamma higher near expiry?
Less time to expiry means small underlying moves can quickly push the option ITM or OTM, swinging delta sharply.
How can I reduce gamma risk?
Trade further OTM strikes, longer expiries, or use spread strategies to cap gamma exposure.
Does gamma matter for buyers?
Yes — long options benefit from positive gamma during sharp directional moves.
